SB 761 
.R4 
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SB 751 
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Copy 1 



REMARKS ON 



The Insect Defoliators 



OF OUR SHADE TREES. 



MADE BY 



DR. C. V. RILEY, U. S. Entomologist, 

Before the New York Farmers, at a Meeting held March lo, 1887,'! 
and Reported by James W. Tooley. 



PP.l.Vl 

GLOBE STATIONERY & I'KINTING CO,, 

89 LiBRRTv Street, 

Nbw Yokk. 






B7fey 




T a meeting of the New York Farmers, held March loth, 1887, at the 
Hotel Brunswick, New York, Dr. C. V. Riley, having been intro- 
duced to the society by the Hon. John Jay, spoke as follows: I am 
afraid, that I shall find some difficulty in entertaining you. to-night 
on this subject of " Injurious Insects," for of all subjects, it seems 
to me, it is the most prosaic and the least calculated to excite 
mirth or sentiment or to form the topic ot an after dinner talk. 
It is always the unexpected that happens and a few days ago 
I little thought of being here addressing a lot of city farmers on such 
a subject. I was then unfamiliar with the personnel of the club and I 
am both pleased and surprised to find that there are a few persons present 
here to-night whom I have known before. There is my friend, Professor 
Lintner, who has done so much good entomological work and who is 
serving 3'ou so faithfully and efficiently as your State Entomologist. There 
is Dr. Loring whom I had the pleasure to serve under during the four 
years of his administration of the National Department of Agriculture 
which he advanced by breadth of culture and public spirit and which he 
graced by his presence as he does such festive boards as this before us. 
There is Mr. Depew whom I had the honor to journey with on a Cunarder 
in 1884 and who, I am glad to see, does not find politics, railroads and 
farming antagonistic, at least in post prandian hours, and who will, let us 
hope, be induced to bring in Momus to offset the sad and dreary current of 
what I may say. 

The subject of "Injurious Insects" is a vast one, and cannot be 
properly dealt with in the limited space that will be at my command. I 
have been somewhat puzzled even to know just what to say — ^just what 
insects to talk about among the multitude that are injurious to our crops. 
Informed by Mr. Peliew, through whom your President urged me to be 
present, that I should be at liberty to choose my own subject I came pre- 
pared to talk a little upon the relation of insects and flowers, thinking that 
that subject might interest you as much as any other, since you all have 
something to do with flowers and there is a very interesting and fascinating 
connection between them and insects. But upon consulting a little with 
Mr. Jay and hearing the opinions of one or two others, I have learned that 
perhaps you expect, and will be more interested in, some remarks upon the 
insects that injuriously affect the trees that are ordinarily used as city shade 
trees, especially as I understand that Prof. Lintner will follow on the in- 
sects injurious to fruit trees. For that reason I will take a few of these for a 
text, and may premise that there is not a single insect that would not occupy 



more than half-an-hour to be properly treated of in all its habits and phases. 
I shall, therefore, confine myself to those more particularly that defoliate 
the trees, leaving out of view the borers and those that affect the root and 
the branch and the blossom. By way of introduction, and assuming that 
most of you are neophytes in economic entomology, let me state a few gen- 
eral truths. As I have elsewhere written, insects play a most important 
part in the economy of nature. The average townsman, accustomed only 
to troublesome household pests, can scarcely appreciate their numbers, their 
diversity in form and habit, or their importance. As scavengers and pol- 
lenizers of our plants and fruits, they not only vitally concern man, but, 
philosophically considered, are essential to his very existence. They sup- 
ply us with the sweetest of sweets, our very best inks and dyes, our finest 
robes, lace and waxes, to say nothing of their use as food (and few who 
have not studied the subject have any just idea of the importance of insects 
and their products as articles of food !) But the benefits which man derives 
from insects must always appear trifling compared with the injury they 
inflict on our agriculture. In the primitive condition of vegetation, as the 
hand of man first found it, insects took their proper place in the economy 
of nature and rarely preponderated in any direction to the injury of the 
wild plants, scattered, for the most part, sparsely throughout their range. 
Harmony between organisms, in the sense of the widest inter-relation and 
inter-dependence, had resulted in the long course of ages. But civilized 
man violated this primitive harmony. His agriculture, which is essentially 
the encouragement and cultivation in large tracts of one species of plant to 
the exclusion of others, which he denominates weeds, gave exceptional fa- 
cilities to the multiplication of insects, which naturally feed on such plants. 
In addition to this, many others have been unwittingly imported from other 
countries, chiefly through commerce ; for it is a most significant fact, that 
the worst weeds and the worst insect pests of American agriculture are im- 
portations from Europe. Thus, in addition to the undue increase of our 
native species, we have to contend with these introduced foreigners, for, as 
compared with Europe, America, as your own Dr. Asa Fitch long since re- 
marked, is the land of insects. Insects probably outnumber in species all 
other animals combined, some 350,000 having already been described, and 
fully as many more remaining yet to be — I won't say discovered, but — 
characterized. And the proper and conscientious characterization of some 
species of microscopic insect involves as much labor as of one of the higher 
animals. Of the above number a good proportion are injurious to vegeta- 
tion. Our associate on my left, Mr. Lintner, has estimated that there are 
156 species that attack the apple alone, in one part of the tree or the other, 
either the fruit, blossom, trunk, branch or the root. 

Let me now keep more strictly to my text. The insect defoliators of 
our shade trees consist chiefly of four species. They are : ist. The imported 
Elm leaf-beetle {Galeriica xantliemelcena). 2d. The so-called Bag Worm 
with the very long name of (Tliyridoptcryx ephcinenvfonnis), sometimes 
called also the Drop Worm; 3d, The White-marked Tussock-moth {Orgyia 
leucostigma), and 4th, the Tall Web-worm {Hypliantria ained). I will briefly 



give you the princip.il facts connected with these four insects, though it is 
very difficult to do so intelligently without diagrams. No. i,the imported 
Elm leaf-beetle is a little yellowish beetle, with two stripes on the elytra, 
and which you all probably know from appearance. It is not more than 
one-fifth to one-eighth of an inch in length. It winters over as a beetle, 
hibernating in all sorts of sheltered places, in the holes of trees, in our posts 
and fences, under the loose bark of trees, in outhouses, in barns, in bedrooms 
even — any sheltered situation that it can find, and also under the leaves of 
our forest trees to a very limited extent. As soon as spring opens, it leaves 
its winter retreat, takes to wing, for both sexes are winged, and speeds to 
the trees on which it feeds and on which it lays its eggs. These trees are 
exclusively the elms and it is very partial to the European elm. The 
female lays her eggs upon either the upper or under side of the leaf, but 
■chiefly on the under side, in a double row of from 15 to 20 eggs each, each 
egg being yellowish elongate and pointed at free end. From these eggs 
there hatch the larva or worms which feed upon the trees, eating at first 
the mere epidermis, leaving the pai'enchyma, and causing the leaves to look 
rusty and sere, — and finally, as they grow older, eating holes through the 
leaves. We all know the appearance of elms that are infested or injured by 
these pests. The beetle, as well as the larva, feeds on the leaf, but it is the 
larva that chiefly does the damage. This insect is multiple-brooded, i. e., 
produces several generations during the year, so that its work can be seen 
throughout most of the summer months, and from the middle of May to the 
end of the growing season is noticeable. The larva descends from the tree 
chiefly by crawling down the trunk, but sometimes lets itself drop, and 
transforms at the surface of the ground or just underneath the ground to a 
pale yellowish pupa, naked, without cocoon, and in a couple of weeks 
becomes a beetle. These beetles lay eggs for another generation and so 
on. This species is an importation from abroad and did not originally 
occur in this country. Insect No. 2, the Bag Worm has a very interesting 
life-history, and an hour might profitably be given to it alone. During the 
winter season, there may be noticed hanging from the bare branches of our 
trees the weather-beaten cases or bags of this insect. If you cut them open, 
you will find the great proportion of them empty, but some will contain 
eggs — a brown shell filled with eggs and the eggs interspersed with a fine 
soft silken down. These eggs hatch, as soon as the leaves put forth, into 
young active worms or caterpillars. The first thing the young worm does 
upon hatching is to begin to make a house for itself, and it is a most amusing 
thing to watch it at this work. First of all, it spins a belt of silk, and after 
having formed the belt it gets over on the further side of the belt, puts its 
head under the belt and makes a perfect somersault, bends up and loosens 
the belt and then spins a second belt, extends the ends and finally joins 
them so as to form a circle. It then forces this ring of silk round the neck 
and by spinning more and more silk to the base at last pushes the little ring 
of silk up until it has formed a perfect cone. As soon as that is formed, it 
begins feeding. The cone is carried upright for some time, but as the worm 
increases in size, the bag or cone becomes too heavy and is allowed to drop. 



Not to be too particular as to details, this worm in time acquires ful! 
growth, seals up its bag and fastens it securely to the tree or branch, so as 
not to be carried down to the ground by the fall of the leaf, Here the 
worm transforms to the pupa state. The male pupa is small, shows evidence 
of future wings, and in due course of time, an active four winged 
moth, black-bodied and glossy-winged, issues from the end of the 
silken bag. The female pupa shows no trace of wings and in fact the 
perfect female is a wingless and legless creature of very degraded character 
biologically speaking. She partially issues from the end of the pupa case> 
but remains in the bag, and the male by a telescopic provision of the genital 
organ is enabled to reach her within it. Fertilization takes place, and the 
eggs are laid in the case or puparium where the}' remain during the winter 
protected and secure. This insect is single brooded. The female is, as I 
have said, perfectly wingless and can never travel awa}' from the tree on 
which she was born, or on which her bag or cone is first fastened. 

We next come to No. 3 — the White-marked Tussock-moth. This is, 
I believe, in this city and in most of the cities of this State, one of the worst 
of your shade tree insects. It is the species which produces that beautiful 
hairy caterpillar which you have all doubtless noticed in Central Park and 
which in years gone by was extremely injurious there — a beautiful 
creature — entomologically considered, of course — with bright, yellow 
brushes upon the back with longer tufts of black, and with a coral-red head 
and coral-red tubercles on the back. This caterpillar is hatched from eggs 
which have passed the winter not inside but on the outside of the cocoon, 
fastened to the trees — and as a rule to the trunks ot the trees. The male ot 
this species is also fully winged, the wing being brown, with a large white 
spot from which it gets its specific name. The female is, on the contrary, 
wingless, and she issues only from her cocoon to crawl on the outside of it 
and there lay her eggs. She covers those eggs with a substance that 
hardens and protects them. There are two generations every year and the 
second generation winters in the egg state on the outside of the cocoons, 
which you can see today plastered on the larger trees in Central Park or 
in the city. 

The fourth insect I mentioned is the one that you seem to be most 
concerned about — the Fall Web Worm. Last year, there was a phenomenal 
increase or advent of it. It is the worm that webs the leaves and the twigs 
and the branches of the tree and absolutely defoliates it, causing it to present 
a very unsightly appearance and doing a great deal of harm. This insect 
hibernates, not in the egg state or in the perfect state as the three others that 
I have mentioned do, but in the pupa state. At the present time, it can be 
found in all sorts of sheltered situations within its cocoon as a chrysalis. . 
As soon as the leaves are about full formed or in the month of May, there 
issue from these chrysalides certain white millers or moths. Both sexes 
are winged and therefore both readily fly. The female lays her eggs upon 
the under side of the leaf in a serrate mass. They are pale yellowish, 
very prettily sculptured and in a very few days hatch into young cater- 
pillars, which are social and gregarious from the start and live within a 



web, gradually increasing- the web as they increase in size until they 
encompass the whole branch and sometimes a very large portion of a tree 
that is small. There are two broods of this insect, the last brood hatching 
in early August in the Southern States and hibernating as a chrysalis, but 
in the north there is some reason to believe there is only one. 

Thus we have four insects concerned in defoliating our shade and park 
trees and they have very different habits and very different characteristics. 
Let me summarize. We have one, a beetle, perfectly capable in both sexes 
of flying, producing several generations during the year, wintering as a 
beetle and therefore very difficult to manage in the winter season. In fact, 
we can practically do nothing with it during the winter, because first, the 
beetles are hidden in out-of-the-way places where we cannot reach them, 
and, secondly, if we could destroy them within the city limits, we co'uld not 
prevent them from flying in from the suburbs in the summer season. But 
with the bag worm, everything can be done in the winter season. There 
we have an insect that hibernates in the egg state in pods which are easily 
discerned on the branches of the bare trees. There is, therefore, no excuse 
for the increase of this pest, for it is a pest in the cities further south, though 
you are comparatively free from it in New York. In Richmond and 
Washington it is especially troublesome. It can be destroyed by burning 
or, preferabl}', by collecting the bags and depositing them in an open space. 
There are a number of parasites that affect this species and I have always 
urged that on pruning the twigs containing these bags, instead of being 
burned, they should be gathered together and left in a mass in some 
pasture away from trees so that the parasites which are also found in these 
cocoons may mature. If the bags are allowed to lay on the ground until 
midsummer, these parasites will issue as winged creatures and fly away to 
destroy other bag worms, while the young worms that hatch from the eggs, 
with very restricted and limited powers of locomotion must inevitably 
perish before they can reach any tree on which they can feed. 

With the Tussock moth, much can also be done in the winter season 
because its cocoon and the eggs upon it are found upon the trunks of the 
trees and undoubtedly the brushing of the trees or the crushing of the 
egg masses, so far as thev can be reached, may be effected very largely. 
I might state in addition that this insect is particularly numerous in the 
older States where the trees are larger. It seems to have a preference for 
the larger trees. It is not numerous in Washington City at present, at least 
on the younger trees. It is particularly abundant in Boston and in 
Philadelphia it is the chief insect found on trees. It is very abundant in 
Albany also, as Dr. Lintner knows, and has been so in Central Park. It is 
rather difficult to reach because it not only spins its cocoon upon the lower 
portions of the trunk, but all over the trunk and limbs. 

The fourth species I have described, the Web-worm was, as I have said, 
the most destructive of all last year. Throughout the New England States 
and on all the Atlantic coast, it had a phenomenal increase and m Washing- 
ton City, it became the " caterpillar nuisance." This can also be dealt with 
in some degree in the winter season. It hibernates in all sorts of sheltered 



places, such as the caves of houses or in the angles of tree boxes. It can 
measurably be reduced by searchiug for and destro3'ing the cocoons and 
chrysalides during the winter. 

There is fortunately one remedy that applies to all four of these insects 
alike, and whether or not we attem[)t to prevent their ravages by destroying 
them in the winter time, we may, after they have got to work, successfully 
and thoroughly and economically and cheaply protect our trees by the use 
of the different arsenites. Every one of these four insects feeds by devour- 
ing the leaves in the larva state, and in the case of No. i in the beetle state 
as well, and they are all amenable to the same treatment— in other words 
the spraying of the trees with a solution of arsenic in any form will verj' 
effectually destroy all four species as soon as they hatch. Allow me to read 
here a few lines from Bulletin No. lo of the Entomological Division of the 
Department of Agriculture, now being printed on this subject of spraying. 
" From the natural history facts already given it is clear that they all 
begin their work very much at the same season or as soon as the leaves are 
fairly developed, and arsenical mixtures properly sprayed on the trees 
about the middle of May and repeated once or twice at intervals of a fort- 
night later in the season, will prove an effectual protection to trees of all 
kinds. This can be done at small expense, and will prove the salvation of 
the trees. An apparatus can be readily constructed, such as has been used 
on the grounds of the Department of Agricullure, on a sufficiently large 
scale to economize time and labor. It should consist of a water tank 
mounted on a cart and furnished with a strong force pump operated by one 
man and furnished with two sets of rubber tubing of a sufficient length (a 
hose reel can be constructed on top of the cart), each hose supported by a 
bamboo extension pole with a cyclone nozzle at tip. With such an appar- 
atus as this three men could drive along the streets and thoroughly spray 
two trees simultaneously ; while if it were found advisable, four independent 
tubes and four men to work them could be employed with a sufficiently 
powerful pump, and thus expedite the work. The details of the more 
important devices connected with this tank-cart are given in my official 
reports. The bamboo ' extension pole ' is used simply to stiffen the rubber 
hose and to enable the operator to elevate the spraying nozzle into the 
center of the tree and spray to a so much greater height. The same result 
can be accomplished by means of a brass rod or gas pipe, in sections, and 
this has the advantage of superior strength, and will consequently carry a 
heavier nozzle or a bunch of nozzles at the end. 

" The ' cyclone ' or ' eddy-chamber ' nozzle is better suited for wdrk 
of this kind on small trees than any yet in use. It is small, simple, cheap, 
will not clog, and gives an admirable spray. A combination nozzle 
ma)' be made of several of these which will be readily supported by the 
section rod and will throw a more profuse spray. 

'• The arsenical compound known as London purple is, as already 
shown, perhaps preferable to white arsenic or Paris green in that it is not 
so liable to burn the leaves while its color enables one to readily distinguish 
poisoned from non-poisoned trees. Moreover it is very cheap. From one- 



quarter to three-quarters of a pound of this substance should be used to a 
barrel of water, and with this quantity of water it is best to mix three 
quarts of cheap or damaged flour which will serve both to render the 
mixture adhesive to the leaves and also to lessen the tendency of the poison 
to burn the leaves. Three-quarters of a pound to the barrel may prove too 
strong a mixture for delicate and susceptible young trees, and it will be 
best for general application to make the amount from three-eighths to one- 
half poiHid to the barrel. Paris green will require a somewhat heavier dose 
— say from one-half to one pound per barrel of water." 

I am now referring of course to city shade trees and my remarks apply 
to streets where there are long rows of trees to protect. If you only have 
a few trees, you need not go to the expense of a cart or tank but a mere 
barrel that will hold a sufficient amount of water can be used, so long as 
you have a force pump and the spraying attachment. This last is novel 
and I should like to show you how it works, but that is not practicable 
here. It consists of a little disc into which the water is forced tangentially 
by means of a force pump so as to be made to revolve at an intense rate in 
a cyclonic course and it issues through a central orifice on the upper 
portion of the disc, and is detachable, so as to permit the cleaning of any 
impediment or the removal of any obstruction that may get into it. 
Through the minute orifice a spray is formed so fine tliat it can be scattered 
on the under side of the trees without dropping and so as to prevent wash- 
ing away by rains. Any respectable firm dealing in colors sell the London 
purple, and a pound costing not more than five cents, can be placed in So 
or loo gallons of water and can be sprayed on the trees. 

Mr. Otis : Is it absolutely necessary to use the purple or the Paris 
green ? 

Prof. Riley ; Some form of arsenic. 

Mr. Otis ; I have been told that simply washing the trees well with 
water by means of a garden engine will wash the beetles off. 

Prof. Riley : It is useless to wash the beetles oft' because other beetles 
will fly in. You want to kill the beetle and kill its young. One pound of 
arsenic and one pound of sal. soda boiled in one gallon of water till the 
arsenic is dissolved and diluted at the rate of one quart to 40 gallons of 
water will answer as well as London purple and Paris green. The chief 
merits of arsenic are cheapness and solubility. Its demerits are its color 
which makes it liable to be mistaken for harmless compounds. Paris green 
has been more extensively used than any other arsenical compound and is 
on the whole one of the most useful. The only advantage the London 
purple has for tree purposes is that it is of a different color to the leaf and 
therefore you can better judge when a tree is properly sprayed ; secondly, 
it is cheap ; thirdly, it is more soluble ; and fourthly, as far as absolute 
experiment goes, it is really more efficient. On the Department grounds 
we had an excellent opportunity of testing, for we have there almost every 
species of elms cultivated, from the imported or European to the several 
indigenous varieties. The beetle shows some preferences and on one 
occasion 1 remember distinctly I took half of the trees of each species and 



8 

treated them and left the other half untouched, as an evidence to Mr. 
Sanders, the superintendent of the grounds, of the efTect of our treatment 
and the trees treated were green for the first time in many )'ears in the 
middle of the summer, while those not treated were destroyed. While this 
beetle has its preferences, yet when numerous, there is no elm absolutely 
free from its attacks. 

Mr. Pellew : Is there an}' tree free from the ravages of all these four 
insects named ? 

Prof. Riley : Oh yes. For instance, to be specific, I will say that the 
Elm-leaf beetle is confined to the elms and attacks no other genus of plants. 
The Bag worm is a very general feeder, but at the same time, it is more 
injurious to conifers or evergreens than to deciduous trees. The Tussock 
moth has a decided preference for the larger and older elms and the 
maples — the soft maple it is attracted to particularly, I think — and never 
occurs on conifers. It is fond also of the horse chestnut and several other 
trees that might be named. The web worm is also a very general feeder 
but has a great predilection for the box e\dcr {Acer St'/^iindo) and I would 
never advise the planting of that tree in any city liable to its attacks. But 
it is not partial to the other maples. The soft, the sugar, the Norway and 
the silver maples are rarely affected by ii. It is fond of the poplars and the 
willows. There are some trees that are never touched by any of these 
insects, but these are trees which the municipal authorities seldom think of 
planting. We are all creatures of habit and most of our gardners are 
Scotchmen or Englishmen, who come here with the notions they imbibed at 
home, and they have introduced the foreign trees and have often neglected 
indigenous ones. Our sweet gum and tulip tree are never attacked by 
insects, and there are no more beautiful trees in the world, whether for 
autum foliage or for general beauty of growth. There is also the sour gum 
and quite a number of other trees that are perfectly free from any of these 
four insects and that ought to be tried in preference to the trees often 
planted. 

Mr. Dinsmore: I had some maples that had millions of pure white flies 
beneath the leaves. 

Prof. Eiley: They are probably perfectly harmless things — May flies. 
That is a phenomenon totally outside of the question we are considering. 
They will never do you any mischief. May flies feed in the larva state in 
water and simply come there to settle just as they do on the windows of 
houses. 

Mr. Fellew: Do either or any of these four insects attack the ends of 
the boughs and bore into them so that the boughs break off? 

Prof. Riley : No, sir ; that is an entirely difficult thing. My friend, 
Dr. Lintner, will I hope touch on some of the fruit insects. I want to say a 
few words further about white-washing trees. I do not know whether that 
is the custom in New York City, but in Washington, the authorities, 
though they have never given any attention to the subject, have the idea 
that white-washing frees the trees from some of these insects. In reality, 
there is only one of the four insects that can be in any way thus affected 



9 

and that is the Tussock moth. So far as the white-washing reaches, a 
certain number of the cocoons will be loosened and exposed to the rains or 
rubbed off by the brushing, and it may possibly be that the lime will affect 
them though there is no evidence that such is the case. But it is of no 
earthly use against the Bag worm or the Elm leaf-beetle or the Web worm, 
and if it must be done at all, there is no reason why the authorities should 
not at least color the lime so as to cause it to resemble a little more nearly 
the color of the trunk of the tree. Of course, I will not discuss the matter 
from an aesthetic standpoint, yet while to some it may not be unpleasant to 
see a lot of trees white-washed, I for one do not like to see it. I may even 
add that so far as the insects I have mentioned are concerned, it is an 
injury. Every one of those insects, with the exception of the first has a 
number of enemies and parasites, many of which have been discovered but 
very recently. For example, up to the present year, no parasites were 
described or recorded as affecting the Web worm, but I now know of quite 
a number. Among such enemies there is the so-called wheel-bug {Priono- 
tus Cristatus) a creature that is best characterized by a peculiar serrate 
cog-wheel on the back of its head, and that is further peculiar in using 
turpentine in cementing together its eggs. This creature destroys the 
caterpillars both of the Tussock-moth and the Web worm. Then there is 
the parasite, Perilitus Communis^ an interesting point about which is that it 
forms a little brown cocoon, attached by a silken thread, and these cocoons 
are sometimes so numerous on the outside of the trunk of the trees which 
have been injured by this Web worm that the trees present a very marked 
appearance. Another point I want to make en passant is that the English 
sparrow has been noticed to peck away at these cocoons of the parasites 
but never to attack the caterpillar itself. The white-washing does harm in 
destroying some of these parasites and also in destroying the egg masses of 
spiders that also attack the caterpillars. 

As to the tree boxes, while they may be necessary on account of the 
injury that without them, horses and other animals as well as mischievous 
boys would inflict upon the trees, at least until these have attained a certain 
size, they are always harmful. They injure the trees by chafing and by the 
pressure of the bandages, and when of wood, as they are in the city of Wash- 
ington, they are particularly injurious, because they serve as nidi for 
different insects. If the laws cannot be made so strict as to prevent injury 
from horses or lads, then I would advise the use of round iron boxes. 

I wish also to say a few words with reference to birds and especially 
in regard to the English sparrow, because there is a prevalent opinion, 
more or less sentimental, that the English sparrow helps us in our warfare 
against these defoliators. In point of fact, there is not one of the four 
insects mentioned but has some protection against most birds. The Elm- 
leaf-beetle is never attacked by birds because of an offensive odor. The 
Eag worm is effectually protected by its tough bag of silk. The Orgyia is 
effectually protected by its hairs and these are more or less mixed in the 
cocoons and the Hyphantria by both its hairs and web. A few native birds 
are known to attack the last two. The yellow-billed and black-billed cuckoos, 



10 

the scrccch-owl, the common robin, and the Baltimore oriole have been 
known to attack them occasionally, but the English sparrow, which is the 
'bird we should look to for assistance because of its prevalence in our cities 
is the very bird that has never been known to attack any one of them, and 
I believe that it is the increase of the English sparrow that has been 
indirectly the cause of the increase of these insects, for by preying upon the 
smooth green worms which are not so troublesome and never were, they 
have given opportunity and room for these hairy worms to multiply. It is 
a very general law in nature that if you take away one species of organism 
you give an opportunity for another organism to take its place and in this 
way, the increase of the Web-worm and of other insects which the sparrow 
does not touch, is indirectly due to the increase of that bird in our cities. 
Another reason also why they are more injurious — for it is true that none 
of these insects are as injurious in the woods as in the cities — is the protec- 
tion they get by tree boxes and the shelter of our houses. 

Mr. Pellevv: To what is the decrease in the measuring worm due, if 
not to the sparrow ? 

Prof. Riley : Partly to the fact that it has been effectually exterminated 
in all the older cities, like Boston and Cambridge, by man, who has band- 
aged the trunks with tar. That has been very effectual, 1 have no doubt, 
because it is just as abundant yet in orchards that have not been so treated. 
The second cause is probably the English sparrow. The English sparrow 
is said to feed on the canker worm in the breeding season. I cannot say it 
is so. I do not know of any absolute observations which are reliable which 
will give us the positive fact that the English sparrow does feed upon the 
canker worm, though as it is a smooth worm and has no protective 
property, either by odor or hairs, it is probable that the sparrow will take 
it. But the other and worse hairy pests have increased. In the case of the 
canker worm, we have an insect which was very troublesome and defoliated 
■ the trees in early spring just as soon as the leaves were out, but in the 
beginning of May here, or by the end of May in the New England States, it 
vanished, entering the ground and remaining there in the chrysalis state all 
through the summer, fall and the winter months until the next spring. In 
the case of this Tussock moth, we are troubled with it all through the 
growing part of the year. In other words, we have exchanged for a species 
which was single-brooded and which occurred only in the larva state for a 
limited period, a hairy caterpillar which is double brooded and occurs all 
through the summer and autumn and which further forms its cocoon above 
ground and disfigures our houses and trees by the masses of these cocoons 
formed upon them. I had intended to make some remarks on imported 
insects and on the importance of the knowledge of the habits of insects, 
but have already occupied too much time. I think this last however, is 
pretty well illustrated in connection with the insect you have asked me 
about — the Elm-leat-beetle, because it is an historical fact that many years 
ago the city fathers of Baltimore found their elm trees being defoliated and 
blighted just as those in Cambridge were, and learning that the people of 
Cambridge were using troughs of oil around their grand elms, as a protec- 



1 1 



tion, went to work and ordered similar troughs to be put around their own 
trees. But it did not help. What was the reason ? In Cambridge, the 
trees were suffering from the canker worm, {Paleacrita vernatd) which in 
the female state is wingless and has to climb up the tree. Therefore these 
oil troughs or bandages of tar impeded her progress and the leaves were 
protected. But in Baltimore, they were troubled with the Elm-leaf-beetle 
■with very different habits. This shows the importance of knowing just 
what you have to deal with and I might extend and elaborate this argu- 
ment to show you how important it is to prevent the introduction of 
foreign pests. I have incidentally stated that all our worst pests and worst 
weeds are importations from Europe. Just now in Australia they are 
suffering from a plague of rabbits, introduced from Europe and we are 
almost threatened with their importation from that country although we 
have been free from the European rabbit as a direct importation for three 
centuries. It would be a greivous pest and a cargo was actually shipped to 
San Francisco and had to be stopped by the authorities. My friend on the 
right mentioned in conversation that he had such a hatred of England that 
he thought he would introduce the mosquito there. Alas, as I know to my 
sorrow, it is already colonized in some parts of London, for I never suffered 
more from it than in the Grosvernor Hotel. I do not know of anything 
that cauld be done to produce more injury to the United States than the 
introduction of some of the plagues from foreign countries that now annoy 
them. For instance, take the tsetse fly in Africa. If it were introduced 
here, it would probably be more disastrous than any army of foreign 
soldiers bent on war, because our stock would vanish before it just as is the 
case in Africa. In California to-day the fruit growers are suffering 
grievously from a pest {Iceryapurchasi) that was introduced from the 
southern hemisphere. It probably originated in New Zealand, was 
introduced from there to Australia and from Australia to Cape Colony, 
and from either Cape Colony or Australia to California. It is to-day more 
injurious to the fruits generally of California than all other insects, and if it 
gets east, it will prove more injurious than any we now have. You know 
the history of the grape phyllo.xera. What has not France suffered from 
its ravages? I strongly urged in 1871 the prevention of its introduction 
into California from the Eastern States or from France, but the advice was 
unheeded and the Napa and Sonoma valleys have suffered from it a 
thousand fold more than the necessary cost of officers to stop it. In 
Connecticut, you have to day a new pest of the pear, which seems as yet 
to be limited to a very small area. It is a European insect, unknown any- 
where else in this country and ruins the pear crop wherever it spreads. It 
could be now probably suppressed if the Department of Agriculture had 
the power to defray the expense of suppressing it. But there is no such 
authority. What is the consequence? It may spread over the country 
just as the cabbage worm did, and just as many others of these pests are 
now pushing over the country. It is an important matter and you in the 
city of New York, the great harbor of the country can probably in the 
future do more to prevent the introduction and the spread westward all 



12 

over the country of foreign pests of tliis kind than the people of any other 
port or city. I do not see why, because these creatures are small in size 
and apparently insignificant, they should not be dealt with in the same way 
as the diseases of domestic animals. You do not hesitate to vote millions 
to exterminate pleuro pneumonia and I maintain that the introduction of 
foreign diseases in the way of insects is equally important, for though it 
does not appeal to your pocket so directly, it in the end does as much harm. 
The ravages of injurious insects in this country in the aggregate foot up 
to enormous sums and have been variously estimated at from ;j30o,ooo,ooo, 
to $400,000,000 annually, taking the whole United States together. Past 
losses from introduced species have been enormous enough to justify 
precautionary measures. 



